JPS5818397B2 - Solvent-free polyurethane coating composition - Google Patents

Description

[Detailed description of the invention] The present invention relates to a solvent-free polyurethane coating composition.

More specifically, the present invention relates to a polyurethane paint composition for metals that is easy to apply as a paint and has excellent drying properties and physical properties, particularly corrosion resistance.

Traditionally, synthetic resins for paints used in areas where corrosion resistance is strongly required, such as port facilities, ships, bridges, and buried steel pipes for gas and water services, include epoxy resins, tar epoxy resins,
There are polyurethane resins, vinyl resins, etc.

Each of these synthetic resin paints has its own characteristics and has been put to practical use as a corrosion-resistant paint, but on the other hand, various drawbacks have been pointed out as described below, and those skilled in the art have strongly requested improvements. .

That is, the drying of the paint film of epoxy paints is extremely slow at low temperatures and high humidity, and it is difficult to use them at temperatures below 5°C or relative humidity above 85%.

General polyurethane paints have chemical resistance, mamo resistance,
Although it has excellent weather resistance, it has less adhesion to metal than epoxy paints, and as a result, its corrosion resistance is inferior.

Vinyl paints have poor heat resistance, chemical resistance, and light resistance, and also have defects in adhesion.

Furthermore, these paints, with the exception of tar-based paints, are generally used after being diluted with a solvent, so the paint film is thin when applied in multiple coats, and several coats are required to achieve a coating thickness of around 200 μm, which is sufficient for corrosion resistance. This is disadvantageous in terms of process, construction period, cost, etc.

In addition, when using paints, there are many places with poor ventilation such as indoors or inside tanks, so solvent-free paints are recommended from the standpoint of human health, the risk of ignition, and the prevention of air pollution caused by solvents. Type paint is highly desired.

On the other hand, tar-based paints can be used as solvent-free paints, can be applied thickly, and have excellent anti-corrosion properties, but questions have been raised regarding the human health of tar, and they are limited to black colors only. There is a flaw.

As described above, the paints used as anti-corrosion paints dry quickly even at low temperatures, have excellent adhesion, and
It is desirable to have water resistance and chemical resistance, be able to be colored in various colors, be easy to apply, and be solvent-free.

Therefore, the main purpose of the present invention is to eliminate the defects of conventional synthetic resin paints, and it relates to a novel solvent-free polyurethane paint composition that fully satisfies the above-mentioned required performance.

More specifically, a mixed polyol 50-90% by weight of castor oil (hereinafter % represents weight%) and 40-10% of a compound having a total average molecular weight of 400 or less and containing 2-4 hydroxyl groups in the molecule. Epoxy modified product 50 obtained by reaction of 90% epoxy compound and aliphatic monocarboxylic acid
- a mixture consisting of 10% organic polyisocyanate H
B), pigment and optionally other additives (Q), the total average functional group number of the mixed polyol is 2.15-2
．． The invention relates to a solvent-free polyurethane coating composition characterized in that the total average molecular weight/total average number of functional groups is in the range of 90-300.

Generally speaking, the composition that provides the best physical properties of a polyurethane paint is a solvent-based two-component paint consisting of a polyester polyol and an organic polyisocyanate. The high viscosity of polyols makes them impractical for actual painting operations.

That is, ■ The viscosity that can be used as a coating machine is generally 1000
Limited to 0 cps/25°C or less.

(2) On the other hand, when low-molecular polyester polyols or general polyether polyols are used, the viscosity of the coating composition is reduced to a workable level, but the adhesion of the coating film is low and the corrosion resistance is poor.

■ More importantly, when a general polyester polyol or polyether polyol is used, air bubbles are generated in the coating film, and these bubbles remain even after the coating film is cured (hereinafter referred to as
(This is called foaming), making it impractical for practical use.

Possible causes of foaming are as follows.

In other words, air bubbles include physical bubbles such as air contained in recesses on the surface to be coated, air entrained during mixing of the composition, trace amounts of water contained in the composition, and moisture in the outside air. There are chemical bubbles created by the carbon dioxide gas generated by the reaction with the inocyanate group, but in the non-solvent type, chemical bubbles are the main cause due to the reaction between the moisture in the outside air and the isocyanate group.

In the case of solvent-based paints, the vapor of the solvent covers the paint film and cuts off the contact between the paint film and the outside air, which prevents reactions between the outside air moisture and incyanate groups. Even if the isocyanate groups react and generate carbon dioxide gas, it will escape from the thin coating along with the solvent vapor.

This can be considered in the same way in the case of physical bubbles, and as a result, a coating film in which no bubbles remain is obtained.

On the other hand, in the case of a solvent-free type, since there is no solvent vapor, the coating film comes into direct contact with the outside air and absorbs moisture.

As a result, the absorbed moisture reacts with the isocyanate groups to generate carbon dioxide gas, resulting in foaming.

Furthermore, since the coating film is thicker and the composition viscosity is higher than that of solvent-based coatings, it is also difficult for generated carbon dioxide gas and physical bubbles to escape from the coating film.

The purpose of using a catalyst is to give priority to the reaction between polyol and isocyanate groups over the reaction between moisture and isocyanate groups, and to prevent foaming, although there are some differences depending on the type of catalyst. It is difficult to put it into practical use because it simultaneously promotes the reaction between water and incyanate groups.

As described above, solvent-free polyurethane paints used for corrosion prevention have improved the above-mentioned drawbacks, namely: (1) The paint composition must have a viscosity low enough to be workable.

■ Excellent physical properties of the paint film, especially good corrosion resistance ■ No air bubbles remaining in the paint film.

However, we have not yet obtained anything that fully satisfies these conditions and can be used industrially.

Therefore, the composition of the present invention is a novel polyurethane paint that has the excellent anticorrosive properties of an epoxy paint and satisfies the above three conditions.

Next, the method for producing the solvent-free polyurethane coating composition of the present invention will be described in detail, but in order to make the content of the present invention easier to understand, first, the characteristics of each composition will be briefly explained.

Castor oil is hydrophobic and is effective in preventing foaming since it prevents the coating composition from absorbing moisture, and also imparts water resistance and flexibility to the coating film.

The total average molecular weight is 400 or less, with 2 to 4 hydroxyl groups in the molecule.
The use of compounds containing these compounds gives appropriate hardness and strength to coatings that are too soft with castor oil alone.

Epoxy modified products provide paint films with the excellent adhesion of epoxy to metal surfaces, improving corrosion resistance, and the higher fatty acids used in them have the effect of preventing foaming of paint films. bring.

As will be described later, the mixing ratio of each composition is determined within a range that provides the coating film with overall excellent performance and good workability as a coating material.

The castor oil used in the present invention is refined castor oil and modified castor oil.

The proportion of castor oil in the mixed polyol is 60-90
Must be in the % range.

When it is less than 60%, the effect of castor oil mixing becomes small and the coating film foams.

If it exceeds 90%, the coating film will not foam, but the coating film will become too soft and the anti-corrosion performance will deteriorate.

Compounds having a total average molecular weight of 400 or less and containing 2 to 4 hydroxyl groups in the molecule that can be used in the present invention include ethylene glycol, propylene glycol, ethylene glycol, diethylene glycol, diethylene glycol, glycerin, and trimethylic acid.

There are monomolecular polyhydric alcohols such as roll propane, monomolecular polyhydric alcohols such as these, and addition reaction products of tofuropylene oxide and ethylene oxide such as ethylenediamine, triethanolamine, and tolylene diamine, which can be used alone or in combination. can.

The proportion of this compound in the mixed polyol is 40 to 1
Must be in the 0% range.

That is, if it is greater than 40%, foaming of the paint film cannot be prevented;
When it is less than 10%, corrosion resistance decreases.

In the present invention, the mixed polyol of castor oil and a compound having a total average molecular weight of 400 or less and containing 2 to 4 hydroxyl groups in the molecule has a total average functional group number (hereinafter referred to as 7) of 2.1.
Range of 5 to 2.65, total average molecular weight/total average number of functional groups (
It is desirable that M/f (hereinafter referred to as M/f) is in the range of 90 to 300, preferably in the range of 140 to 240.

Coatings obtained using mixed polyols within this range have moderate hardness and excellent properties, especially excellent corrosion resistance. Performance will be significantly degraded.

7 and M/f of the present invention are specifically calculated as follows.

where X: Part by weight of castor oil used to obtain the mixed polyol M: Average molecular weight of castor oil f: Average number of functional groups of castor oil Each polyol a1, a2...a
Each weight part of n ml, m2, °°°゛°°mn: each polyol a1,
a2, °°.

・・・・・・Molecular weight of an fl, f2, °°°"°°fn: each polyopoly1, a
2, ... is the number of functional groups of an.

In the present invention, the epoxy compound used to obtain the epoxy modified product has two epoxy groups in one molecule, and there is a diglycidyl ester type represented by the general formula, and these compounds may be used alone or in combination. However, among these, bisphenol A type is particularly effective.

On the other hand, examples of aliphatic monocarboxylic acids used to obtain epoxy-modified products by reacting with these compounds having two epoxy groups in one molecule include oleic acid, linoleic acid, ricinoleic acid, and coconut oil fatty acids. These can be used alone or in combination.

In this case, it is not preferable to use dicarboxylic acid or trienoic acid because the viscosity of the epoxy modified product obtained increases or gelation occurs.

Epoxy modified products made from these carboxylic acids and epoxy compounds can be obtained by conventionally known methods, such as heating an epoxy compound with a carboxylic acid without a catalyst or in the presence of a catalyst to open the epoxy group and esterify it. .

In this case, the carboxyl group is 0.4
-1.05 chemical equivalents, and the reaction is preferably carried out so that the reaction rate of the carboxyl group is 97% or more.

Moreover, in order to maintain the storage stability of the obtained epoxy modified product, a polymerization inhibitor such as quinones can be used.

Mixed polyol and epoxy modified product are mixed to form a mixture (
A) is obtained, in which case the proportion of the epoxy modified product in the mixture (A) is in the range of 10-50%, preferably 1
A range of 0-30% is desirable.

Epoxy modified product has higher viscosity than mixed polyol by 50%
The thicker the hole, the higher the viscosity of the mixture hole, causing problems in painting work, making the paint film more likely to foam, and reducing the physical properties of the paint film.

Moreover, when it is less than 10%, the mixing effect of epoxy becomes small, and the corrosion resistance of the coating film decreases.

The vine organic polyisocyanate (B) used in the present invention includes diphenylmethane diisocyanate, polyphenylmethane polyisocyanate, partially carbodiimidized diphenylmethane diisocyanate, tolylene diisocyanate, and partially modified polyisocyanates with hydroxyl group-containing compounds. There are prepolymers, which can be used alone or in combination of two or more.

Examples of the hydroxyl group-containing compound in this case include monomolecular polyhydric alcohols, oils and fats such as castor oil, modified products thereof, polyester polyols and polyether polyols having a molecular weight of 200 to 2,000 and having two or more hydroxyl groups. It can be used alone or in combination of two or more.

Pigments that can be used in the present invention include those known in the art, such as extender pigments such as talc, clay, baryta powder, silica powder, alumina, and calcium carbonate, and colored pigments such as iron oxide, titanium oxide, and carbon black. These can be used alone or in combination of two or more.

Except in special cases, the pigment is generally mixed and dispersed in the mixture (A) of polyols etc. by a well-known method, but the amount used is preferably in the range of 10 to 70% of the total composition. It is important to dry thoroughly before using.

Incidentally, the pigment can also be mixed and dispersed in the organic polyisocyanate.

Various other additives that can be used in the present invention include those known in the art, such as thixotropic agents, plasticizers, antioxidants, ultraviolet absorbers, leveling agents, dehydrating agents, and the like.

In order to actually use the solvent-free polyurethane coating composition according to the present invention, the incyanate group to hydroxyl group ratio is 0.90.
: 1.0-1.50 : 1.0 range, preferably 0.95 : 1.0-1.30 : 1.0 range, mA and organic polyisocyanate) (B)
The mixture may be mixed at room temperature or under slight heating, coated on a substrate, and then cured at room temperature or under heating.

Since the composition of the present invention is solvent-free, it can improve the various defects caused by the use of solvents and tar in conventional paints, and can completely eliminate the drawback of foaming of the coating film, which is unique to polyurethane paints. became.

Furthermore, it is now possible to apply thick coatings and obtain sufficient anti-corrosion performance with just one coat.

Therefore, the composition of the present invention can be used in fields that require corrosion protection, such as port facilities, ships, bridges, and buried steel pipes for gas and water.

Hereinafter, specific embodiments of the present invention will be described using examples and in comparison with comparative examples, but it should be understood that the present invention is not limited thereto.

In addition, parts in the examples mean parts by weight.

Corrosion resistance was measured in Examples by making a cross cut approximately 111 m wide in the coating and immersing it in warm water at 50°C.

For the test, the immersed sample is taken out, water droplets are wiped with filter paper, and the sample is air-dried for 30 minutes.

Next, when a thin-blade razor is inserted between the coating film and the surface to be coated from the cut part, the number of days required until the razor can be easily inserted two times is shown.

Example 1 608 parts of bisphenol A epoxy (Epicor 1004 manufactured by Shell Petrochemical) in a 2J flask and 30 parts of xylene
392 parts of oleic acid was added dropwise to the mixture, and the mixture was reacted at 160-200°C to obtain an epoxy modified product having an acid value of 2.8.

(Xylene was removed by post-treatment) Next, 20.0 parts of this epoxy modified product and 60.0 parts of castor oil were added.
0 parts, dipropylene glycol 20.0 parts, talc 80
．． 1 part of titanium, 8.9 parts of titanium, and 250 parts of toluene were added to this mixture.
It was dispersed to become

This product was heated under reduced pressure to azeotropically remove toluene and water in the system to obtain a base agent.

Next, the main agent and curing agent (carbodiimide-containing diphenylmethane diisocyanate, NCO content 28%) were added at 60%
'C, mixed with a two-component airless sprayer (manufactured by Matco) at a weight ratio of 1:0.4, and coated on a mild steel plate (film thickness 200μ). Shown in the table.

In this example, the value is -2,2, -=-170.

[Example 2 A coating film was prepared in the same manner as in Example 1 except that iron oxide, talc, and titanium were used instead of talc and titanium, and the following formulation was used.

Blending prescription/Main ingredient Epoxy modified product obtained in Example 1 20.0 parts Castor oil
60.0, dipropylene glycol 20.0 iron oxide
40.0 talc 40
．． 0 titanium 9.0; hardening agent carbodiimide-containing diphenyl 76.5-tone tomethane diisocyanate The physical properties of the coating film obtained with this formulation are shown in Table 1.

T and = in this example are the same as in Example 1.

Example 3 A coating film was prepared in the same manner as in Example 1 except that polyphenyl 1-methane polyisocyanate (Coronate MR, manufactured by Nippon Polyurethane Co., Ltd.) was used as the curing agent.

The measurement results of the physical properties of this coating film are shown in Table 1.

In this example, the values are the same as in Example 1.

1, f Example 4 In Example 1, P instead of dipropylene glycol
A coating film was prepared using P-200 (manufactured by Sanyo Kasei Co., Ltd.) in the same manner as in Example 1 except for the following formulation.

The measurement results of the physical properties of this coating film are shown in Table 1.

Combination prescription Main agent Epoxy modification obtained in Example 1.

. , o-sound μ castor oil 66.7PP-200
13.3 Talc 69.8 Titanium
78 Curing agent carbodiimide-containing diphenyl 53.7 sound b methane diisocyanate
Example 5 Bisphenol A epoxy (Epicote 1004) 7
43 parts of xylene, 30 parts of xylene, and 257 parts of ricinoleic acid were reacted in the same manner as in Example 1 to obtain a modified epoxy product with an acid value of 0.7.

Using this epoxy modified product, a coating film was prepared in the same manner as in Example 2 except for the above.

The measurement results of the physical properties of this coating film are shown in Table 1.

In this example, 伪 and : are the same as in Example 1.

Example 6 Bisphenol A epoxy (Epicote) 828
444 parts (manufactured by Shikuru Petrochemical), 556 parts of ricinoleic acid,
An acid value of 2.6 was obtained from 30 parts of xylene in the same manner as in Example 1.
An epoxy modified product of was obtained.

Using this modified epoxy product, a coating film was prepared in the same manner as in Example 1 except for the following formulation.

The measurement results of the physical properties of this coating film are shown in Table 1. Formula: Main ingredient: Epoxy modified product: 15.0 parts Castor oil
70.8PP-20014,2 Talc 74.2 Titanium
8.2 Curing agent carbodiimide-containing diphenyl 92.2 parts Methane diisocyanate (2) -2,4, -, -=240 in this example.

Example 7 Epicote 1004.392 parts, caproic acid 208.2 parts
An epoxy modified product was obtained from 30 parts of xylene in the same manner as in Example 1.

Using this epoxy modified product, a coating film was prepared in the same manner as in Example 1 except for the above.

The measurement results, such as the physical properties of the coating film, are shown in Table 1.

EE*Mf! IK Oyu 6 □ Oyo, Tomoe yo Real Example 1 Ooyu.

The compositions of Examples 1 to 7 provided coating films with excellent corrosion resistance.

Comparative Example 1 A coating film was prepared in the same manner as in Example 1 except that dipropylene glycol was not used and the following formulation was used.

Combination prescription Main agent Epoxy obtained in Example 1.

,. Partially modified castor oil 60.0 talc
57,6 titanium
6.4 Curing agent Carbodiimide-containing diphenyl 40.0 Methane diisocyanate There were no bubbles in the resulting coating film, but the corrosion resistance was poor at only 1 day, making it impractical.

This is -2.7, -==350 in this comparative example.

Comparative Example 2 A coating film was created in the same manner as in Example 1 except that castor oil was not used in Example 1 and the following formulation was used.

Combination prescription Main agent Epoxy obtained in Example 1.

6. . Sound degenerate GP-400 (manufactured by Sanyo Chemical Co., Ltd. 75.0) Talc 51. O titanium
5.7 Curing agent Carbodiimide-containing diphenyl 91.0 Methane diisocyanate Countless small bubbles remained in the resulting coating film, and it was not suitable for practical use.Furthermore, the corrosion resistance of the coating film was 1 day.

This is -3,0, -==130 in this comparative example.

Comparative Example 3 A coating film was prepared in the same manner as in Example 1 except that the modified epoxy product was not used and the following formulation was used.

Compounding formula Main ingredient GP-600 (manufactured by Sanyo Kasei Co., Ltd. '6 o, oon B) Castor oil 40.0 Talc
672 titanium
75 Diphenyl containing curing agent carbodiimide 74.1 Methane diisocyanate Many bubbles remained in the resulting coating film, and the corrosion resistance was poor at only 1 day, making it unusable for practical use.

In this comparative example, f=2.9, -=-=240.

Comparative Example 4 Using the modified epoxy product obtained in Example 1, a coating film was prepared in the same manner as in Example 1 except for the following formulation.

Combination prescription Main agent Epoxy obtained in Example 1.

,. Otosu modified castor oil 40.0 Dipropylene glycol 40.0 Talc
742 titanium
8.2 Curing agent Carbodiimide-containing diphenylene 112.4 methane diisocyanate Many small bubbles remained in the resulting coating film, and it was not suitable for practical use.

M This is -2,1, -==-110 in this comparative example.

Comparative Example 5 An attempt was made to create a coating film using the following formulation, but the viscosity was high and spray coating as in Example 1 was not possible.

Combination prescription Main agent 56. Epoxy modification obtained in Example 1.

Onshi body massage oil 25.0 Dipropylene glycol 20.0 parts Talc
79゜2 titanium
8.2 Curing agent carbodiimide-containing diphenyl 80.6 Methane diisocyanate This comparative example is -2.1, knee 120.

Claims (1)

[Scope of Claims] 1 (A) Castor oil 6 C) - Mixed polyol 50-90 with 90% by weight and 40-10% by weight of a compound having a total average molecular weight of 400 or less and containing 2-4 hydroxyl groups in the molecule
% by weight, and a mixture consisting of 50-10% by weight of an epoxy modified product obtained by the reaction of an epoxy compound and a fatty acid monocarboxylic acid; (B) an organic polyincyanate; and (Q a pigment and other additives as necessary); The total average number of functional groups of the mixed polyol is in the range of 2.15-2.65, and the total average molecular weight/total average number of functional groups is 90-
300.